One of the main findings derived from the analysis of the Neandertal genome was the evidence for admixture between Neandertals and non-African modern humans. An alternative scenario is that the ...ancestral population of non-Africans was closer to Neandertals than to Africans because of ancient population substructure. Thus, the study of North African populations is crucial for testing both hypotheses. We analyzed a total of 780,000 SNPs in 125 individuals representing seven different North African locations and searched for their ancestral/derived state in comparison to different human populations and Neandertals. We found that North African populations have a significant excess of derived alleles shared with Neandertals, when compared to sub-Saharan Africans. This excess is similar to that found in non-African humans, a fact that can be interpreted as a sign of Neandertal admixture. Furthermore, the Neandertal's genetic signal is higher in populations with a local, pre-Neolithic North African ancestry. Therefore, the detected ancient admixture is not due to recent Near Eastern or European migrations. Sub-Saharan populations are the only ones not affected by the admixture event with Neandertals.
The changes of chromosomal inversion polymorphism composition of
Drosophila subobscura
in samples from Apatin (Serbia) were studied in a 24-years interval (1994–2018). The variation was significant ...for all autosomes and directional, increasing the inversions considered as ‘warm’, whereas those reported as ‘cold’ decreased. Furthermore, the Chromosomal Thermal Index (
CTI
), which allows studying the thermal adaptation of the whole karyotype increased significantly in that period of time. These results were in agreement with the indicators of global warming in Apatin: a trend to increase of the mean, maximum and minimum (this latter even significant) temperatures, and an erratic pattern of rainfall (also usual in global warming). The deviations from the Wright–Fisher model of genetic drift were used to consider the possible effect of migration or selection as evolutionary factors responsible for the change in inversion frequencies. To quantify approximately the rate of change in the frequencies, for each kind of inversions (‘cold’, ‘warm’ and ‘non-thermal adapted’), the difference in frequency between the Apatin samples obtained in 1994 and 2018 was computed and then it was divided by the number of years elapsed. This rate was always higher (from twice as many as thirty times more depending on the autosome) for thermal adapted inversions (‘cold’ or ‘warm’) than the ‘non-thermal’ adapted. From this study, it could be concluded that the chromosomal inversions of
D. subobscura
could change (in composition and frequencies) in a predictable direction and a rather ‘rapid’ rhythm to adapt to the global warming scenario.
Drosophila has demonstrated to be an excellent model to study the adaptation of organisms to global warming, with inversion chromosomal polymorphism having a key role in this adaptation. Here, we ...introduce a new index (Chromosomal Thermal Index or CTI) to quantify the thermal adaptation of a population according to its composition of "warm" and "cold" adapted inversions. This index is intuitive, has good statistical properties, and can be used to hypothesis on the effect of global warming on natural populations. We show the usefulness of CTI using data from European populations of D. subobscura, sampled in different years. Out of 15 comparisons over time, nine showed significant increase of CTI, in accordance with global warming expectations. Although large regions of the genome outside inversions contain thermal adaptation genes, our results show that the total amount of warm or cold inversions in populations seems to be directly involved in thermal adaptation, whereas the interactions between the inversions content of homologous and non-homologous chromosomes are not relevant.
Drosophila subobscura
is a species with a rich chromosomal polymorphism which is adaptive to different climatic conditions. Five samples of the Font Groga population (Barcelona, Spain) were sampled ...in autumn during 5 consecutive years (2011–2015) to obtain their inversion chromosomal polymorphism, and climatic data of several meteorological variables were also collected. The aim was to analyze the adaptive potential of inversions with regard to climatic variables, being the most relevant: mean temperature (T
mean
), maximum temperature (T
max
), minimum temperature (T
min
), humidity (Hm) and rainfall (Rf). As expected, no significant variation in inversion frequencies were detected over this short period of time. However, from a climatic point of view it was possible to differentiate ‘warm’ and ‘dry’ from ‘cold’ and ‘humid’ samples. The joint study of maximum (T
max
) and minimum (T
min
) temperatures was a key element to understand the effect on adaptation of many inversions. It was also observed that temperature had to be considered in conjunction with humidity and rainfall. All these factors would condition the biota of
D. subobscura
habitat, and chromosomal inversions could provide an adaptive response to it.
Using a well-adapted Drosophila subobscura population (Avala, Serbia), a drastic experiment of inbreeding was carried out to assess whether the expected level of homozygosity could be reached or if ...other evolutionary forces affected the process. In general, no significant changes of inversion (or arrangement) frequencies were detected after 12 brother–sister mating generations. Furthermore, no significant differences were obtained between observed and expected (under the inbreeding model) karyotypic frequencies. Thus, these results seemed to indicate that the main evolutionary factor in the experiment was inbreeding. However, in the G₁₂ generation, complete chromosomal fixation was reached only in two out of the eight final inbred lines. In these lines, the chromosomal compositions were difficult to interpret, but they could be likely a consequence of adaptation to particular laboratory conditions (constant 18 °C, food, light period, etc.). Finally, in a second experiment, the inbred lines presented higher fertility at 18 °C than at 13 °C. Also, there was a significant line effect on fertility: inbred line number 6 (A₁, J₁, U₁₊₂; U₁₊₂₊₆, E₈, and O₃₊₄₊₇) presented the highest values, which maybe the result of an adaptation to laboratory conditions. Thus, the results obtained in our experiments reflect the adaptive potential of D. subobscura inversions.
Drosophila subobscura is a species with a rich chromosomal polymorphism for inversions. Evidence demonstrates that it is adaptive. In the present research, we studied whether it is possible to detect ...changes in the inversion chromosomal polymorphism of D. subobscura in a medium-term period of time. The Serbian population of Avala was selected and its inversion composition in 2004 and 2011 (a seven year period) was compared. Signicant variation was found in the U chromosome. This result was due to a signicant increase of U1+2 (warm) and a decrease of Ust (cold) and U1+2+6. Further, minimum, maximum and mean temperatures increased (although not signicantly). Thus, U chromosome seems to be able to react in a medium-term to temperature changes in the way expected by the global warming.
One of the main findings derived from the analysis of the Neandertal genome was the evidence for admixture between Neandertals and non-African modern humans. An alternative scenario is that the ...ancestral population of non-Africans was closer to Neandertals than to Africans because of ancient population substructure. Thus, the study of North African populations is crucial for testing both hypotheses. We analyzed a total of 780,000 SNPs in 125 individuals representing seven different North African locations and searched for their ancestral/derived state in comparison to different human populations and Neandertals. We found that North African populations have a significant excess of derived alleles shared with Neandertals, when compared to sub-Saharan Africans. This excess is similar to that found in non-African humans, a fact that can be interpreted as a sign of Neandertal admixture. Furthermore, the Neandertal's genetic signal is higher in populations with a local, pre-Neolithic North African ancestry. Therefore, the detected ancient admixture is not due to recent Near Eastern or European migrations. Sub-Saharan populations are the only ones not affected by the admixture event with Neandertals.
FS-Q, SC, CA and CL-F are supported by a grant from the Ministerio de Ciencia e Innovación of Spain (BFU2009-06974) and CGL2010-14944/BOS.
We have analysed the distribution of post mortem DNA damage derived miscoding lesions from the datasets of seven published Neandertal specimens that have extensive cloned sequence coverage over the ...mitochondrial DNA (mtDNA) hypervariable region 1 (HVS1). The analysis was restricted to C-->T and G-->A miscoding lesions (the predominant manifestation of post mortem damage) that are seen at a frequency of more than one clone among sequences from a single PCR, but do not represent the true endogenous sequence.
The data indicates an extreme bias towards C-->T over G-->A miscoding lesions (observed ratio of 67:2 compared to an expected ratio of 7:2), implying that the mtDNA Light strand molecule suffers proportionally more damage-derived miscoding lesions than the Heavy strand.
The clustering of Cs in the Light strand as opposed to the singleton pattern of Cs in the Heavy strand could explain the observed bias, a phenomenon that could be further tested with non-PCR based approaches. The characterization of the HVS1 hotspots will be of use to future Neandertal mtDNA studies, with specific regards to assessing the authenticity of new positions previously unknown to be polymorphic.
Based on the experience of a course taught by the authors, this paper seeks to show that an adequate use of IT in the teaching of a Business Etchics (BE) course depends on clarifying the assumptions ...about ethics and the place of the course within a programme. For this purpose it explains how IT can be used to strengthen a view of BE based on dialogue and mutual learning and it encourages the combination between virtual and face-to-face teaching. Finally, the paper examines the relationship between the use of IT, individual learning processes and communities of practice.
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